1. Field of the Invention
The present invention relates to a connecting structure to a cell of an electrical voltage detecting connector which is connected to a fuel cell constituted by laminating plural cells having an anode and a cathode, for detecting electrical voltage of the cell, and to a fuel cell.
Priority is claimed on Japanese Patent Application No. 2004-235153, filed Aug. 12, 2004, and Japanese Patent Application No. 2004-235154, filed Aug. 12, 2004, the contents of which are incorporated herein by reference.
2. Description of Related Art
In recent years, fuel cells are attracting attention as a new source of power, such as for an automobile. In general, a fuel cell consists of a membrane electrode architecture (MEA) in which an anode electrode (negative electrode) and a cathode electrode (positive electrode) are disposed on either side of a solid polymer electrolyte membrane respectively, and a pair of separators which contain the membrane electrode architecture therebetween. When this fuel cell is operated to generate electricity, it generates an electrochemical reaction by supplying gaseous fuel (for example, hydrogen gas) to the anode electrode of the fuel cell, and supplying oxidizing gas (for example, air containing oxygen) to the cathode electrode. Since only harmless water is generally generated when generating electrical power, the fuel cell attracts attention from a viewpoint of influence on the environment or use efficiency.
Incidentally, it is difficult to obtain electric power sufficient to drive an automobile from one fuel cell. It has been investigated to mount a fuel cell which has a stack structure in which plural cells each of which is formed by interposing a membrane electrode architecture between a pair of separators are layered, in an automobile, such that sufficient electric power to drive the automobile can be supplied.
In this case, in order to monitor whether a cell which constitutes a fuel cell is generating electricity normally, it is very important to detect the voltage of the cell. From such a viewpoint, a fuel cell provided with terminals for measuring voltage is proposed.
For example, patent document 1 (Japanese Unexamined Patent Application, First Publication No. H09-283166) discloses technology in which a circular hole is formed in the carbon plate of each cell, and one end of an output terminal is connected to the circular hole using a banana clip, and another end of an output terminal bundle with a voltage measuring apparatus is connected through a connector.
Moreover, patent document 2 (Japanese Unexamined Patent Application, First Publication No.2003-86219) discloses technology of clipping a terminal holder which holds terminals disposed on separators of cells of a fuel cell, thereby making the terminals unmovable.
Moreover, cross sections of the principal part of a fuel cell and of a voltage detecting connector which is connected to the fuel cell are shown in FIG. 5. As shown in this figure, a fuel cell 30 consists of a predetermined number (in this case, n) of cells 31, which are stacked. Each cell 31 is interposed between separators 33 and 34 in a membrane electrode architecture 32. In each cell 31, terminals 35 and 36 for measuring electrical voltage are disposed on the separator 33 at an anode electrode side and the separator 34 at a cathode electrode side, respectively. A cell connecting device 39 is connected to the fuel cell 30 thus constituted. The cell connecting device 39 is equipped with a predetermined numbers of connectors 37 and 38, whereby the electrical voltage of the separators 33 and 34 disposed at the terminals 35 and 36 can be detected by contacting the connectors 37 and 38 with the terminals 35 and 36, thereby, detecting electrical voltage in each cell.
However, hitherto, there were the following problems. That is, in the conventional art, as explained above, referring to FIG. 5, in general, each terminals 35 and 36 of the fuel cell 30 are arranged in series in the same position when they are looked at from a direction of layering. However, in order to mount the fuel cell 30 in a vehicle etc., it is required to reduce the thickness of each cell 31 to as thin as possible, and the gap between the terminals 35 and 36 tends to become narrow inevitably in connection with this.
As a result, when the terminals 35 and 36 are arranged in series, the gap between the terminals 35 and 36 becomes narrow, and there is possibility of interference with the connection of the connectors 37 and 38, if for example, the gap between the cell connecting devices 39 provided with the connectors 37 and 38 cannot be maintained sufficiently, and as a result, the cell connecting devices 39 come into contact with each other, etc.
Moreover, since it is necessary to stack a lot of cells 31 in order to obtain a required output in the case in which the fuel cell 30 is mounted in a vehicle, if the terminals 35 and 36 are disposed on all of the separators 33 and 34 of each cell 31, the weight will increase to an extent that cannot be ignored because of the terminals 35 and 36, and the cost will increase.
Next, cross sections of the principal part of a fuel cell and of a voltage detecting connector which is connected to the fuel cell are shown in FIG. 10, as is disclosed in, for example, the patent document 3 (Japanese Unexamined Patent Application, First Publication No. 2002-352820). As shown in this figure, a fuel cell 130 consists of a predetermined number (in this case, n) of cells 131, which are stacked. Each cell 131 is interposed between separators 133 and 134 in a membrane electrode architecture 132. In each cell 131, a terminal 135 for measuring electrical voltage is disposed on a separator 133 at an anode electrode side. A cell connecting device 139 is connected to the fuel cell 130 thus constituted. The cell connecting device 139 is equipped with a predetermined number of connectors 137, whereby the electrical voltage of the separators 133 disposed at the terminals 135 can be detected by contacting the connectors 137 with the terminals 135, thereby detecting electrical voltage in each cell.
However, there are the following problems in the prior art. That is, hitherto, as explained referring to FIG. 10, because a terminal is disposed on the separator of one electrode (for example, an anode electrode), in order to detect the cell voltage of one cell, the monitoring is performed ranging over the separator of the electrode shared with the adjoining cell. As a result, in the case of detecting the cell voltage of the end cell of a stacked body in which plural cells are stacked, there is no cell adjoining thereto, and it is impossible to detect the cell voltage of the end cell. Therefore, in order to detect the cell voltage of the end cell, as shown in FIG. 10, it is necessary to dispose a cover plate (dummy separator) 140 having the same shape as a separator (separator at the side of an anode electrode) 134, on the end of the stacked body of cells and to dispose a terminal 141 for a connector 142 on the cover plate 140. Thus, it is necessary to dispose separately, a separator, a terminal, and a connector, which are not related to power generation, and the number of parts increases, thereby increasing cost, stacking width, and weight.